Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: FRIDAY, February 10, 1995 TAG: 9502100105
SECTION: NATIONAL/INTERNATIONAL PAGE: A-3 EDITION: METRO
SOURCE: Associated Press
DATELINE: WASHINGTON LENGTH: Medium
Dr. F.M. Uckun of the University of Minnesota, Minneapolis, said Thursday the ``smart bomb'' actually is an antibody that will attach to a receptor molecule found only on the surface of leukemia cells.
``The antibody is the missile,'' said Uckun, and hooked to the missile is the payload - a chemical that actually kills the leukemia cell.
``Normal tissue is not affected,'' he said. ``Only the leukemia cells are going to die.''
Uckun, first author of a study appearing today in the journal Science, said the same ``smart bomb'' technique for the targeted delivery of a killing chemical also can be used for some cancers of the breast, ovaries and brain.
In the study, Uckun and his team injected human leukemia cancer cells into laboratory mice that have no immune system. The cancer, called B-cell precursor leukemia, is the most common form of childhood cancer and the second-most-common form of acute leukemia in adults.
The leukemia cells thrived inside the mice and thus created for the researchers a way of testing the targeted therapy.
Uckun said earlier studies have shown that a molecule called protein tyrosine kinase is essential for the survival of leukemia cells. Studies also have shown that a synthetic chemical called genistein could block the action of the kinase.
But the problem was how to get the genistein inside the cancer cells. And the solution was the ``smart bomb.''
Uckun said that on the surface of the leukemia cells is a molecule receptor called CD19. Experiments showed a laboratory-grown antibody called B43 would attach directly to CD19, but to no other receptor. To make the ``smart bomb,'' the researchers joined the B43 antibody with the cancer-killing genistein.
The ``smart bomb'' was injected into 10 mice with human leukemia and their survival rates were compared with 110 untreated mice with leukemia.
All the untreated mice died within 61 days; all the mice treated with the ``smart bomb'' lived for more than 120 days. Later studies on the treated mice showed that 99.999 percent of the leukemia cells were killed.
Other leukemia-infected mice received chemotherapy of the type now used on humans. Some of the drugs were effective, but none matched the ``smart bomb,'' said Uckun.
He said the findings suggest a treatment that included cycles of first the drugs, then ``smart bomb,'' could be very effective against leukemia.
The technique was developed during research aimed at finding out why some leukemia cells are able to recover from chemotherapy. Although many drugs suppress the cancer for a time, some leukemia cells rebound and the disease progresses, often killing the patient.
B43 teamed with another chemical already has been approved for experimental human use, said Uckun. His group now plans to seek Food and Drug Administration approval to link B43 with genistein and test the drug on human leukemia patients.
by CNB